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Subject: Re: [f2fs-dev] [PATCH v2] f2fs: rename checkpoint=merge mount option
 to checkpoint_merge
To:     Daeho Jeong <daeho43@gmail.com>
CC:     <linux-kernel@vger.kernel.org>,
        <linux-f2fs-devel@lists.sourceforge.net>,
        <kernel-team@android.com>, Daeho Jeong <daehojeong@google.com>
References: <20210202051829.2127214-1-daeho43@gmail.com>
 <ef27f0cc-87b6-cea1-31a6-f2837d6a673c@huawei.com>
 <CACOAw_wGY1CNXZ9QoLB1t0800Wyjv1_P9iuqk4SOKjT-oUQamw@mail.gmail.com>
 <6f1e4639-3715-d855-951d-7c0a67fa9913@huawei.com>
 <CACOAw_zmPXzTrtp7VVyBoYLRe_TRzTB6CqjQkmLq=NU=Bky9WQ@mail.gmail.com>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <ec3685a4-1871-fd69-68ae-1c22066aa06d@huawei.com>
Date:   Tue, 2 Feb 2021 17:13:42 +0800
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On 2021/2/2 17:07, Daeho Jeong wrote:
> If I understand it correctly, the only thing I have to do now is
> remove "nocheckpoint_merge" now.
> Am I correct? :)

For this patch, Yup. :)

Thanks,

> 
> 2021년 2월 2일 (화) 오후 5:30, Chao Yu <yuchao0@huawei.com>님이 작성:
>>
>> On 2021/2/2 16:02, Daeho Jeong wrote:
>>> I chose the same step with "flush_merge", because it doesn't have
>>> "noflush_merge".
>>
>> Oh, "noxxx" option was added only when we set the option by default in
>> default_options(), when user want to disable the default option, it
>> needs to use "noxxx" option, and then we will show this "noxxx" option
>> string to user via show_options() to indicate that "noxxx" option is
>> working now.
>>
>> Anyway I think we should fix to show "noflush_merge" option because we
>> have set flush_merge by default.
>>
>>> Do you think we need that for both, "noflush_merge" and "nocheckpoint_merge"?
>>
>> For "nocheckpoint_merge", we can introduce this option only when we want
>> to set "checkpoint_merge" by default.
>>
>> Here is the example from noinline_data:
>>
>> Commit 75342797988 ("f2fs: enable inline data by default")
>>
>> Thanks,
>>
>>>
>>> I thought we needed to give some time to make this be turned on by
>>> default. It might be a little radical. :)
>>>
>>> What do you think?
>>>
>>> 2021년 2월 2일 (화) 오후 4:40, Chao Yu <yuchao0@huawei.com>님이 작성:
>>>>
>>>> On 2021/2/2 13:18, Daeho Jeong wrote:
>>>>> From: Daeho Jeong <daehojeong@google.com>
>>>>>
>>>>> As checkpoint=merge comes in, mount option setting related to checkpoint
>>>>> had been mixed up and it became hard to understand. So, I separated
>>>>> this option from "checkpoint=" and made another mount option
>>>>> "checkpoint_merge" for this.
>>>>>
>>>>> Signed-off-by: Daeho Jeong <daehojeong@google.com>
>>>>> ---
>>>>> v2: renamed "checkpoint=merge" to "checkpoint_merge"
>>>>> ---
>>>>>     Documentation/filesystems/f2fs.rst |  6 +++---
>>>>>     fs/f2fs/super.c                    | 26 ++++++++++++++------------
>>>>>     2 files changed, 17 insertions(+), 15 deletions(-)
>>>>>
>>>>> diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst
>>>>> index d0ead45dc706..475994ed8b15 100644
>>>>> --- a/Documentation/filesystems/f2fs.rst
>>>>> +++ b/Documentation/filesystems/f2fs.rst
>>>>> @@ -247,9 +247,9 @@ checkpoint=%s[:%u[%]]      Set to "disable" to turn off checkpointing. Set to "enabl
>>>>>                          hide up to all remaining free space. The actual space that
>>>>>                          would be unusable can be viewed at /sys/fs/f2fs/<disk>/unusable
>>>>>                          This space is reclaimed once checkpoint=enable.
>>>>> -                      Here is another option "merge", which creates a kernel daemon
>>>>> -                      and makes it to merge concurrent checkpoint requests as much
>>>>> -                      as possible to eliminate redundant checkpoint issues. Plus,
>>>>> +checkpoint_merge      When checkpoint is enabled, this can be used to create a kernel
>>>>> +                      daemon and make it to merge concurrent checkpoint requests as
>>>>> +                      much as possible to eliminate redundant checkpoint issues. Plus,
>>>>>                          we can eliminate the sluggish issue caused by slow checkpoint
>>>>>                          operation when the checkpoint is done in a process context in
>>>>>                          a cgroup having low i/o budget and cpu shares. To make this
>>>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>>>>> index 56696f6cfa86..d8603e6c4916 100644
>>>>> --- a/fs/f2fs/super.c
>>>>> +++ b/fs/f2fs/super.c
>>>>> @@ -145,6 +145,7 @@ enum {
>>>>>         Opt_checkpoint_disable_cap_perc,
>>>>>         Opt_checkpoint_enable,
>>>>>         Opt_checkpoint_merge,
>>>>> +     Opt_nocheckpoint_merge,
>>>>>         Opt_compress_algorithm,
>>>>>         Opt_compress_log_size,
>>>>>         Opt_compress_extension,
>>>>> @@ -215,7 +216,8 @@ static match_table_t f2fs_tokens = {
>>>>>         {Opt_checkpoint_disable_cap, "checkpoint=disable:%u"},
>>>>>         {Opt_checkpoint_disable_cap_perc, "checkpoint=disable:%u%%"},
>>>>>         {Opt_checkpoint_enable, "checkpoint=enable"},
>>>>> -     {Opt_checkpoint_merge, "checkpoint=merge"},
>>>>> +     {Opt_checkpoint_merge, "checkpoint_merge"},
>>>>> +     {Opt_nocheckpoint_merge, "nocheckpoint_merge"},
>>>>>         {Opt_compress_algorithm, "compress_algorithm=%s"},
>>>>>         {Opt_compress_log_size, "compress_log_size=%u"},
>>>>>         {Opt_compress_extension, "compress_extension=%s"},
>>>>> @@ -946,6 +948,9 @@ static int parse_options(struct super_block *sb, char *options, bool is_remount)
>>>>>                 case Opt_checkpoint_merge:
>>>>>                         set_opt(sbi, MERGE_CHECKPOINT);
>>>>>                         break;
>>>>> +             case Opt_nocheckpoint_merge:
>>>>> +                     clear_opt(sbi, MERGE_CHECKPOINT);
>>>>> +                     break;
>>>>>     #ifdef CONFIG_F2FS_FS_COMPRESSION
>>>>>                 case Opt_compress_algorithm:
>>>>>                         if (!f2fs_sb_has_compression(sbi)) {
>>>>> @@ -1142,12 +1147,6 @@ static int parse_options(struct super_block *sb, char *options, bool is_remount)
>>>>>                 return -EINVAL;
>>>>>         }
>>>>>
>>>>> -     if (test_opt(sbi, DISABLE_CHECKPOINT) &&
>>>>> -                     test_opt(sbi, MERGE_CHECKPOINT)) {
>>>>> -             f2fs_err(sbi, "checkpoint=merge cannot be used with checkpoint=disable\n");
>>>>> -             return -EINVAL;
>>>>> -     }
>>>>> -
>>>>>         /* Not pass down write hints if the number of active logs is lesser
>>>>>          * than NR_CURSEG_PERSIST_TYPE.
>>>>>          */
>>>>> @@ -1782,7 +1781,7 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root)
>>>>>                 seq_printf(seq, ",checkpoint=disable:%u",
>>>>>                                 F2FS_OPTION(sbi).unusable_cap);
>>>>>         if (test_opt(sbi, MERGE_CHECKPOINT))
>>>>> -             seq_puts(seq, ",checkpoint=merge");
>>>>> +             seq_puts(seq, ",checkpoint_merge");
>>>>
>>>> Other noxxx options will be shown in show_options(), how about following them?
>>>>
>>>>>         if (F2FS_OPTION(sbi).fsync_mode == FSYNC_MODE_POSIX)
>>>>>                 seq_printf(seq, ",fsync_mode=%s", "posix");
>>>>>         else if (F2FS_OPTION(sbi).fsync_mode == FSYNC_MODE_STRICT)
>>>>> @@ -1827,6 +1826,7 @@ static void default_options(struct f2fs_sb_info *sbi)
>>>>>         sbi->sb->s_flags |= SB_LAZYTIME;
>>>>>         set_opt(sbi, FLUSH_MERGE);
>>>>>         set_opt(sbi, DISCARD);
>>>>> +     clear_opt(sbi, MERGE_CHECKPOINT);
>>>>
>>>> Why should we clear checkpoint_merge option in default_options()?
>>>>
>>>> Thanks,
>>>>
>>>>>         if (f2fs_sb_has_blkzoned(sbi))
>>>>>                 F2FS_OPTION(sbi).fs_mode = FS_MODE_LFS;
>>>>>         else
>>>>> @@ -2066,9 +2066,8 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
>>>>>                 }
>>>>>         }
>>>>>
>>>>> -     if (!test_opt(sbi, MERGE_CHECKPOINT)) {
>>>>> -             f2fs_stop_ckpt_thread(sbi);
>>>>> -     } else {
>>>>> +     if (!test_opt(sbi, DISABLE_CHECKPOINT) &&
>>>>> +                     test_opt(sbi, MERGE_CHECKPOINT)) {
>>>>>                 err = f2fs_start_ckpt_thread(sbi);
>>>>>                 if (err) {
>>>>>                         f2fs_err(sbi,
>>>>> @@ -2076,6 +2075,8 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
>>>>>                             err);
>>>>>                         goto restore_gc;
>>>>>                 }
>>>>> +     } else {
>>>>> +             f2fs_stop_ckpt_thread(sbi);
>>>>>         }
>>>>>
>>>>>         /*
>>>>> @@ -3831,7 +3832,8 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>>>>>
>>>>>         /* setup checkpoint request control and start checkpoint issue thread */
>>>>>         f2fs_init_ckpt_req_control(sbi);
>>>>> -     if (test_opt(sbi, MERGE_CHECKPOINT)) {
>>>>> +     if (!test_opt(sbi, DISABLE_CHECKPOINT) &&
>>>>> +                     test_opt(sbi, MERGE_CHECKPOINT)) {
>>>>>                 err = f2fs_start_ckpt_thread(sbi);
>>>>>                 if (err) {
>>>>>                         f2fs_err(sbi,
>>>>>
>>> .
>>>
> .
>